Polymers, including copolymers and terpolymers, when isolated from reaction solution are a mixture of compounds of varying composition and molecular weight. Typically they contain small quantities of starting material and by-products which are undesirable in the final polymer. The polymer generally undergoes further processing before its ultimate use. The subject of this invention thus pertains to a method of purifying the polymer, i.e. the crude polymer.
Davidson, in U.S. Pat. No. 5,945,251, discloses a method of purifying polyhydroxystyrene polymers by adding an amine, a hydrophilic solvent, a hydrophobic solvent, and water to the polymer; separating the aqueous phase; then removing the hydrophilic solvent and the hydrophobic solvent to form the purified polymer.
Zempini, et al. in U.S. Pat. No. 5,789,522 and U.S. Pat. No. 5,939,511, extracts impurities from a phenolic resin by dissolving the resin in a photoresist solvent and extracting the water-soluble impurities therefrom.
Sheehan et al in U.S. Pat. No. 6,414,110 B1 discloses a purification of a crude polymer by use of immiscible solvents to remove the low molecular weight polymers from the desired product.